One kind of flat panel display with more application in the present market is the Liquid Crystal Display (LCD). The Liquid Crystal Display comprises a liquid crystal panel and a digital drive circuit. The digital drive circuit outputs the analog voltages to drive the liquid crystal display panel for display. The digital drive circuit comprises a digital to analog conversion module. The digital to analog conversion module achieves the function of converting the inputted digital signals into the analog voltages.
In prior art, the Digital Analog Converter (DAC) module of the liquid crystal display comprises a plurality of divider resistors, a plurality of gate circuits and a plurality of transistors. 3 bit digital drive data is illustrated. FIG. 1 is a circuit diagram of one channel in a 3 bit DAC module. As shown in FIG. 1, each channel comprises 23-1 divider resistors and 23 switch circuits. Each switch circuit comprises 3 transistors and 0 to 3 NOT gate circuits, which has 23*3 transistors in total. Each time, one set of digital signals is inputted, only one switch circuit is conducted, the outputted analog voltage is the divider voltage of the conducted switch circuit. However, in practical usage, the digital drive data of the liquid crystal display is the digital signal of at least 8 bit. Then, each channel of the DAC module requires at least 28*8=2048 transistors. Consequently, the common DAC module with 960 channels requires 960*2048=1966080 transistors. Thus, the amount of the transistors in the DAC module of the liquid crystal display according to prior art is tremendously huge. Not only the hardware cost is higher, and the larger chip area is occupied.